Method of producing photographic representations on aluminum surfaces



Aug. 9, 1938. Y A. JENNY ET AL 2 ,01 METHOD OF PRODUCING PHOTOGRAPHI C REPRESENTATIONS ON ALUMINUM SURFACES Filed April 25, 1954 INITIAL DE COAT/N6 SECOND/4 OXIDE COATING LJGI'IT SE IT/VEI SALTS.

I /v VENTORS Nikolai Buaiz y,

Arron/vs).-

Patented Aug; 9, 1938 METHOD OF PRODUCING PHOTOGRAPHIC REPRESENTATIONS N ALUMINUM SUR- FACES Alexander LJenny, Berlin-Charlottenburg, and

- Nikolai Budiloif, Berlin-Friedenam'Germany,

assignors to Siemens & Halske, Aktiengesellschaft, Siemensstadt, near Berlin, Germany, a corporation of Germany "Application April 25, 1934, Serial No. 722,398 Germany April 25, 1933 Claims. (Cl. 9%)

It has been proposed to produce written characters or photographic representations of various kinds on aluminum alloys. In this process anoxygen-containing layer is formed on the surface of the aluminum or aluminum alloy and the said layer is impregnated with light-sensitive substances. By means of, a copying process or by exposure to light in a photographic apparatus photographs, written characters or any other representations may be produced on the layer prepared as above mentionedand these representations are afterwards made durable by a suitable treatment. r

In order to obtain accurate representations of good definition, it is necessary that the oxygencontaining layer be sufliciently porous to absorb the light-sensitive substances. Furthermore it is necessary that the layer have no -disturbing color. I

well known methods for producing oxygen-con-- taining layers on aluminum or aluminum alloys.-

To give an example an oxalic acid bath and a direct electric current are suitable as his known per se, for producing the oxygen-containing. layer. But in this case the layer has generally a yellowish color and is therefore not proper for photoof certain aluminum alloys, for instance duralumin, a 'glasslike, bright layer can be developed which has also a small power for' absorbing solutions or suspensions oi! light-sensitive substances. Besides such a layer gives 8. spotted photograph "with an unequal distribution of shadow. It has suiilciently. but it has a. matt aspect and no me tallic lustre which is however 0! great importance -ibt,nhotomphic representations in order to reach excellentTclearness and eilectoi space.

Thorough investigations have shown that, on

aluminum or an aluminum alloy, oxygen-coir.

' ready to carrylight-sensitive substances.

taining layers especially suitable for photographic purposes can be produced, according to this invention, ,in the following manner: Any articles of aluminum or an aluminum alloy, say, plates,

foils or films are first dipped in one bath, under conditions producing an oxide coating thereon, and then in a second bath containing other chemical agents, under conditions producing the accession of additional oxide coating. In each bath the aluminum articleis connected as an electrode and subject to the effect of an electric current, flowing through the bath. It is preferred to connect the aluminum articles as anodes to a source of direct current. The best results are somewhat better. if the representation, after being photographicaliy' produced, fixed and toned is filled or coated with oil,-fat or with wax or lac.

I Practical example A polished sheet of aluminum of x 20 square centimetres and a thickness of 0.1 centimetre was treated in 20 per cent chromic' acid solution, connected as anode and subjected to the influence of an electric direct current for minutes. The voltage was 20 volts and the average value of the current intensity 20 amperes. The bath temperature was maintained at 65 C. The cathode was termed by another sheet of aluminum. After washing with water the anodically treated sheet was brought into a 3 per cent oxalic acid solution and, connected as anode, exposed to theaction of a direct current of 48 volts and about 6 amperes for 30 minutes. The bath temperature] amounted to C.

After taking out the sheet of aluminum it was washed with water and dried. The oxygen-containing. layer produced in the two baths is then For instance, .the sheet with the layer canbe impregnated with a solution oi ammonium chloride and then with a solution of silver nitrate. Thereby silver chloride is deposited within the poresof the oxygen-containing layer; After drying a colorlessiayer exists upon which representation posure to light in a photographic apparatus. 'It will be understood that the metallic lustre remains at thosesp tsoi the oxide lsyerwhich are and written characters oi'yerygood quality n 9 be formed by a. copying method or by direct exnot influenced by light during the photographicprocedures. The aspect of the photographic representation is then very good.

The accompanying drawing represents a dia grammatic showing on a greatly enlarged scale of the possible structure of an oxide coated and impregnated photographic plate produced in accordance with our invention. In this showing:

- The part oi -the figure to the left oi! the arrow represents a possible structure of an' aluminum plate after treatment in the first coating bath of our invention, while The part of the figure to the right of the arrow represents a possible structure of the plate. after the second coating operation and after impregnation with photo-sensitive materials.

' In the figures like parts are indicated by like reference numerals. The aluminum or aluminum alloy plate or film is represented by the numeral I. In Fig. 1 this'metalplate orfilm is shown coated with an initial oxide layer 2 interspersed with pores 3. The depth of this layer is indicated between the lines a and b.

Fig. 2 shows a plate or film which has been further subjected to the second anodic treatment of our invention, as well as having been impregnated with photo-sensitive salts or a sensitized emulsion. In this showing the initial oxide coating 2 is represented as having been dissolved to.

some extent by the second electrolytic treatment, the large pores 3 of this initial coating having been partially filled by a second deposit 4 of oxide nature produced in the second electrolytic bath.-

It is therefore assumed that the second oxide layer is deposited in the pores of the initial layer leaving a larger number of smaller pores. And in Fig. 2 these smaller pores are indicated as being filled with light sensitive material 5.

It will be noted that the second oxide layer 4 is indicated in Fig. 2 as extending into the aluminum plate or film'to a somewhat greater depth than the initial coating 2. Also that the top of the initialcoating 2 is shown at a level lower than a. This is, of course, purely hypothetical, since the exact nature and structure of the two coatings is not known. It is known'that the initial layer is porous and that after the second layer has been deposited the coating as a whole presents a somewhat greater metallic lustre and appears to be capable of being impregnated somewhat more uniformly. This is believed to indicate the possibility of thepresence of a larger Y number of finer pores, after deposition of the secand layer.

a direct current can be employed. It is possible to employ a direct current in the first bath and an alternating current in the second bath or vice versa.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim'is:

1. In the process 01 producing photographic representations on articles of aluminum and aluminum, alloys, the steps which comprise treating a sheet of aluminum composition electrolytically in an aqueous coating bath containing chromic acid, under cohditions producing a porous oxide layer'thereon, then treating the resulting oxidecoated sheet electrolytically in an aqueous bath of oxalic acid,-under conditions producing the accession of additional porous oxide coating, and impregnating the resulting coating with photosensitive materials.

2. In the process of producing photographic representations on articles of aluminum and aluminum alloys, the steps which comprise treating a sheet of aluminum composition electrolytically in an aqueous coating bath containing a solution oi chromic acid having a concentrationof about 20 per cent, under conditions producing a porous oxide layer thereon, then treating the resulting oxide. coated article electrolytically in a bath containing an aqueous solution of oxalic acid having a concentration of about 3 per cent, under conditions producing the accession of additional porous oxide coating, and impregnating the resulting coating with photo-sensitive materials.

3. The process of claim 1 wherein the electrolytic treatments are conducted at an elevated temperature, with direct current and with the aluminum article connected as anode.

4. In the production oi! aluminum and aluminum alloy articles having light sensitive surfaces, the process which comprises successively treating such an article electrolytically at elevated temperatures in acid coating baths of two diilerent acids, under conditions producing a porous, double anodic coating of aluminum oxide having a metallic lustre thereon: one of said acid baths containing chromic acid and the other containing oxalic acid; then impregnating the resulting dou-' ble oxide coating with photo-sensitive materials.

5. A sensitized article 01' aluminum composition with a surface bearing a double coating of aluminum oxide-having photo-sensitive materials absorbed in the pores thereof, said coating being porous, being substantially colorless with a metallic lustre, beingresistantto mechanical abrasion and corrosion and having'a high power of absorption for photo-sensitive materials; said photo-sensitive materials being absorbed in said coating in such manner as to produce, upon exposure to light, a photographic reproduction of excellent definition, giving the effect of space.

ALEXANDER JENNY. NIKOLAI BUDILOFF. 

